The excel importer processes all values according to the type excel has stored for it.
There are two ways how excel can show a number with leading zero's. The value can be stored as a string/text. In that case the importer won't have a problem importing the values as they are shown.
Or excel can use a display mask. This means that excel stores that the type is a float, it stores the value as a float (with decimals) and processes it as a flow. But only when displaying the value it will be shown with leading zero's and without decimals. Display masks are for now impossible to apply during the import.
You can use a microflow to format your value. Just create an flow with a float as input and an string as output and format the value as you would like to display it in your project.